Targeted murders and assassinations have long been means used to achieve political or personal ends (or simply to cause chaos). In the 4th century BCE, for example, as Philip of Macedon (Alexander the Great‘s father) was making preparations for crossing into Asia and at the celebration of his daughter’s marriage Cleopatra to Alexander of Epirus, Philip was assassinated by Pausanias, who had a bitter grievance against Cleopatra’s uncle and Philip. A few hundred years later Julius Caesar was felled in a plot by a group of nobles, and in the last two thousand years plus, countless leaders—some heroes and some villains—have been slain by their political opponents: Lincoln, Martin Luther King, Nicholas II, Gandhi (Mohandas, Indira, and Rajiv), JFK, Mussolini, Sadat, Rabin, Bhutto, etc.

Rajiv Gandhi; Terry Ashe—Time Life Pictures/Getty Images

In most instances historically, the assassin hoped to complete the deed and get away, but in modern times a new form of murder and assassination developed: the suicide attack. It was 20 years ago tomorrow, on May 21, 1991, that Rajiv Gandhi, prime minister of India from 1984 to 1989, was assassinated by a suicide bomber from the Liberation Tigers of Tamil Eelam (who were routed in Sri Lanka’s civil war in recent years) while campaigning for upcoming parliamentary elections in the Indian state of Tamil Nadu. In that attack, a woman concealed a bomb in a basket of flowers and was able to get close enough to Gandhi to kill him and 16 others.

Gandhi’s assassination was not the first modern suicide attack, however. The first such attack is usually said to have occurred in Lebanon in 1981, but it was two years later that a suicide attack captured the world’s attention and spread fear throughout the globe. In 1983 there was an attack in Lebanon against the U.S. embassy that killed 63 people and was followed with simultaneous car bombings of U.S. and French military barracks that killed 299.

Since 1983, suicide bombing has become a favourite terrorist tactic of insurgent groups from Sri Lanka to Chechnya to Afghanistan. One indication of this growing preference is the number of attacks, which rose from 1 in 1981 to more than 500 in 2007. The use of suicide bombing has grown for three primary reasons. First, suicide bombing is almost impossible for security forces to prevent. Bombers such as the three second-generation Pakistani Britons and one young immigrant from Jamaica who killed 52 people in the London bombings of 2005 are almost unstoppable once they are committed to die and kill others. Second, suicide bombing generates publicity. Media attention is like oxygen to terrorists, and suicide bombings receive enormous news coverage owing to the willingness of the bombers to die for a cause and the shocking damage inflicted indiscriminately against targets and bystanders alike—as happened in the assassination in 1991 of Indian Prime Minister Rajiv Gandhi and 16 others by a woman associated with the Liberation Tigers of Tamil Eelam. Third, a successful suicide bombing requires little expertise and few resources beyond a bomb and someone willing to carry it. Therefore, for groups determined to spread terror, suicide bombing is much more cost-effective than other tactics such as hostage taking, which requires considerably greater investment in resources, planning, and training. Instruction manuals, videos, and other training materials, some of them available online, have allowed groups like the London bombers to construct bombs with little guidance.

The proliferation of attacks in the last 30 years led Flinders University in Australia to develop a comprehensive database on such attacks. As Flinders University emeritus professor Riaz Hassan discussed in YaleGlobal in 2009, between 1981 and 2006 there were more than 1,200 suicide attacks in the world—or about 4% of the total terrorist attacks. Though they represented just a small fraction of the attacks, nearly 15,000 people died in them—or 32% of the total in all terrorist attacks. Targets were not just political leaders but also military forces and even civilians. (Hassan is also the author of Life as a Weapon: The Global Rise of Suicide Bombings, in which he argues that the volume of deaths and chaos that suicide bombings cause help to account for its increased use. An excellent PDF of some statistics can be found here; for example, between 1981 and 2006, Iraq had the most attacks—651—and the most deaths—6,714—a figure more than triple the areas second-most prone to such attacks, Israel and the Palestinian territories.)

Any violent act seems alien to most of us, and a suicide bombing appears as a wholly irrational act. Then, why has it grown so dramatically and what type of person may be particularly susceptible to becoming a suicide bomber? Unfortunately, the motivations are complex. As Kiras explains, sometimes faith might motivate a bomber, though the Tamil Tigers (and other groups employing suicide methods) were a largely secular ethnic separatist group, so religious motivations cannot be considered sufficient. As Kiras continues:

Studies have shown that many suicide bombers, particularly in developed societies, are not deranged or wild-eyed fanatics with nothing to live for; indeed, a significant number of bombers have come from income and education levels well above their countries’ norms. Another broad trend, noticeable in the numerous suicide bombings in Iraq and Afghanistan, has been the recruitment of individuals who are physically or mentally ill, impoverished, suggestible, or alienated in some way from their society. Individual purposes or motivations can range broadly, from revenge for the death of a family member (for instance, the female suicide bombers, or “Black Widows,” in Chechnya) to outrage against an occupying power (for instance, in Iraq or the Palestinian territories) or against some incident (e.g., the abuse of prisoners at the Abu Ghraib prison in Iraq) to coercion or even the payment of money to one’s family (as has occurred in Afghanistan and elsewhere). Neither altruism nor anomie figures much in such individual calculations.

For many militant groups, suicide bombing is but one tactic in a larger campaign to achieve strategic goals—for example, tying to force a country to withdraw its army by inflicting heavy damage to its forces or in a battle waged against another militant group.

So, what should we do to diminish the possibility of attacks and prevent them? Unfortunately, because the motivations and characteristics of bombers vary, there is no single approach that will work. Sometimes governments may engage in their own targeted assassinations, be it by Israel of leaders of Palestinian militant groups or drone attacks against leaders of al-Qaeda by the United States (or the commando raid by Navy SEALS against Osama bin Laden). Some places, such as Israel, have attempted to build security fences (or secure zones). Setting up checkpoints, be they on highways or in airports, can act as a deterrent by adding another layer of security for the public. Some governments, such as the United States, have tried to aggressively expand surveillance, particularly electronic eavesdropping, to try to thwart attacks, though civil libertarians have raised concerns.

Despite such countermeasures, it is quite difficult to thwart suicide bombers, because as governments adapt to techniques (such as the September 11 attacks and using planes as missiles), suicide bombers develop alternate ways of carrying out assaults. As George W. Bush said in a 2004 debate with John Kerry, in fighting terror “[w]e have to be right 100% of the time. And the enemy only has to be right once to hurt us.” That statement has a lot of resonance, but it was actually quite odd, since it was a paraphrase of a statement made by the IRA in 1984 after a failed attempt on the life of Margaret Thatcher: “Today we were unlucky, but remember we only have to be lucky once. You will have to be lucky always.”